Two-Spinon and Orbital Excitations of the Spin-Peierls System TiOCl

We combine high-resolution resonant inelastic x-ray scattering with cluster calculations utilizing a recently derived effective magnetic scattering operator to analyze the polarization, excitation energy, and momentum dependent excitation spectrum of the low-dimensional quantum magnet TiOCl in the range expected for orbital and magnetic excitations (0 - 2.5 eV). Ti 3d orbital excitations yield complete information on the temperature-dependent crystal-field splitting. In the spin-Peierls phase we observe a dispersive two-spinon excitation and estimate the inter- and intra-dimer magnetic exchange coupling from a comparison to cluster calculations

Selection of DNA nanoparticles with preferential binding to aggregated protein target.

High affinity and specificity are considered essential for affinity reagents and molecularly-targeted therapeutics, such as monoclonal antibodies. However, life's own molecular and cellular machinery consists of lower affinity, highly multivalent interactions that are metastable, but easily reversible or displaceable. With this inspiration, we have developed a DNA-based reagent platform that uses massive avidity to achieve stable, but reversible specific recognition of polyvalent targets. We have previously selected these DNA reagents, termed DeNAno, against various cells and now we demonstrate that DeNAno specific for protein targets can also be selected. DeNAno were selected against streptavidin-, rituximab- and bevacizumab-coated beads. Binding was stable for weeks and unaffected by the presence of soluble target proteins, yet readily competed by natural or synthetic ligands of the target proteins. Thus DeNAno particles are a novel biomolecular recognition agent whose orthogonal use of avidity over affinity results in uniquely stable yet reversible binding interactions

Uncovering human needs through visual research methods: Two commercial case studies

This paper presents two respective case studies which demonstrate how visual research methods can elicit a deep understanding of the needs of potential end users and drive product and service development at a strategic business level.The engagement of users in the development of products, services and systems has been explored by a number of design disciplines in the last few decades including but not limited to product design, human-computer interaction, systems design and service design. Each has recognised the importance of understanding the humans who will potentially be using their design outcome. Notable research methods include ethnographic inspired research, in-context and lab-based observations, interviews and the user trial of prototypes. However, these approaches also have their critics and limitations ranging from the need for incremental adjustment rather than radical design, being time-consuming and costly processes, and the large volume of ‘messy data’ being collected contributing to the complexities of ‘wicked problems’.In response to some of these limitations, a number of research methods have emerged which are more arts-based in nature i.e. the act of creating allows the researcher to extract ‘deeper’ human needs (tacit and latent needs) in a drastically shorter timescale. To fully utilise such approaches it is essential that a study be designed which amalgamates diverse research methods. The two case studies presented in this paper employ a variety of traditional and generative design research methods in live commercial projects. The specific project outcomes are retained under Intellectual Property and, as such, this paper critically focuses on the value of the process and methods utilised, their relationship to the wider concept of arts-based research, and discusses issues related to their application in commercial work

Ordering of the pyrochlore Ising model with the long-range RKKY interaction

The ordering of the Ising model on a pyrochlore lattice interacting via the long-range RKKY interaction, which models a metallic pyrochlore magnet such as Pr_2Ir_2O_7, is studied by Monte Carlo simulations. Depending on the parameter k_F representing the Fermi wavevector, the model exhibits rich ordering behaviors

Revisiting Static and Dynamic Spin Ice Correlations in Ho2Ti2O7

Elastic and inelastic neutron scattering studies have been carried out on the pyrochlore magnet Ho2Ti2O7. Measurements in zero applied magnetic field show that the disordered spin ice ground state of Ho2Ti2O7 is characterized by a pattern of rectangular diffuse elastic scattering within the [HHL] plane of reciprocal space, which closely resembles the zone boundary scattering seen in its sister compound Dy2Ti2O7. Well-defined peaks in the zone boundary scattering develop only within the spin ice ground state below ~ 2 K. In contrast, the overall diffuse scattering pattern evolves on a much higher temperature scale of ~ 17 K. The diffuse scattering at small wavevectors below [001] is found to vanish on going to Q=0, an explicit signature of expectations for dipolar spin ice. Very high energy-resolution inelastic measurements reveal that the spin ice ground state below ~ 2 K is also characterized by a transition from dynamic to static spin correlations on the time scale of 10^{-9} seconds. Measurements in a magnetic field applied along the [1${\bar1}$0] direction in zero-field cooled conditions show that the system can be broken up into orthogonal sets of polarized alpha chains along [1${\bar1}$0] and quasi-one-dimensional beta chains along [110]. Three dimensional correlations between beta chains are shown to be very sensitive to the precise alignment of the [1${\bar1}$0] externally applied magnetic field.Comment: 11 pages, 10 figures. Submitted for publicatio

Temporal Trends in Vertebral Size and Shape from Medieval to Modern-Day

Human lumbar vertebrae support the weight of the upper body. Loads lifted and carried by the upper extremities cause significant loading stress to the vertebral bodies. It is well established that trauma-induced vertebral fractures are common especially among elderly people. The aim of this study was to investigate the morphological factors that could have affected the prevalence of trauma-related vertebral fractures from medieval times to the present day. To determine if morphological differences existed in the size and shape of the vertebral body between medieval times and the present day, the vertebral body size and shape was measured from the 4th lumbar vertebra using magnetic resonance imaging (MRI) and standard osteometric calipers. The modern samples consisted of modern Finns and the medieval samples were from archaeological collections in Sweden and Britain. The results show that the shape and size of the 4th lumbar vertebra has changed significantly from medieval times in a way that markedly affects the biomechanical characteristics of the lumbar vertebral column. These changes may have influenced the incidence of trauma- induced spinal fractures in modern populations

Spectral, mineralogical, and geochemical variations across Home Plate, Gusev Crater, Mars indicate high and low temperature alteration

Over the last ~ 3 years in Gusev Crater, Mars, the Spirit rover observed coherent variations in color, mineralogy, and geochemistry across Home Plate, an ~ 80 m-diameter outcrop of basaltic tephra. Observations of Home Plate from orbit and from the summit of Husband Hill reveal clear differences in visible/near-infrared (VNIR) colors between its eastern and western regions that are consistent with mineralogical compositions indicated by Mössbauer spectrometer (MB) and by Miniature Thermal Emission Spectrometer (Mini-TES). Pyroxene and magnetite dominate the east side, while olivine, nanophase Fe oxide (npOx) and glass are more abundant on the western side. Alpha Particle X-Ray Spectrometer (APXS) observations reveal that eastern Home Plate has higher Si/Mg, Al, Zn, Ni, and K, while Cl and Br are higher in the west. We propose that these variations are the result of two distinct alteration regimes that may or may not be temporally related: a localized, higher temperature recrystallization and alteration of the east side of Home Plate and lower temperature alteration of the western side that produced npOx

Development of a novel 3D culture system for screening features of a complex implantable device for CNS repair

Tubular scaffolds which incorporate a variety of micro- and nanotopographies have a wide application potential in tissue engineering especially for the repair of spinal cord injury (SCI). We aim to produce metabolically active differentiated tissues within such tubes, as it is crucially important to evaluate the biological performance of the three-dimensional (3D) scaffold and optimize the bioprocesses for tissue culture. Because of the complex 3D configuration and the presence of various topographies, it is rarely possible to observe and analyze cells within such scaffolds in situ. Thus, we aim to develop scaled down mini-chambers as simplified in vitro simulation systems, to bridge the gap between two-dimensional (2D) cell cultures on structured substrates and three-dimensional (3D) tissue culture. The mini-chambers were manipulated to systematically simulate and evaluate the influences of gravity, topography, fluid flow, and scaffold dimension on three exemplary cell models that play a role in CNS repair (i.e., cortical astrocytes, fibroblasts, and myelinating cultures) within a tubular scaffold created by rolling up a microstructured membrane. Since we use CNS myelinating cultures, we can confirm that the scaffold does not affect neural cell differentiation. It was found that heterogeneous cell distribution within the tubular constructs was caused by a combination of gravity, fluid flow, topography, and scaffold configuration, while cell survival was influenced by scaffold length, porosity, and thickness. This research demonstrates that the mini-chambers represent a viable, novel, scale down approach for the evaluation of complex 3D scaffolds as well as providing a microbioprocessing strategy for tissue engineering and the potential repair of SCI